4.6.4. Consistent snapshots

Previously, file systems had to be quiesced manually (fsfreeze) before taking a snapshot of active instances for consistent backups.

The Compute libvirt driver automatically requests the QEMU Guest Agent to freeze the file systems (and applications if fsfreeze-hook is installed) during an image snapshot. Support for quiescing file systems enables scheduled, automatic snapshots at the block device level.

This feature is valid only if the QEMU Guest Agent is installed (qemu-ga) and the image metadata enables the agent (hw_qemu_guest_agent=yes).